Known hydrostatic-mechanical transmissions with power branching can comprise two hydrostatic machines constituting hydrostatic transmissions and a mechanical transmission, whereby the transmission input shaft is connected with the hydrostatic transmission as well as with the mechanical transmission and the mechanical transmission is connected with a summing unit for summing the power figure delivered via the drive shaft and via the hydrostatic transmission.
The invention is based upon a state of the art which is found, for example, in the transmission system of the German Pat. Nos. 1,817,764 and 1,188,958. These transmission systems have the disadvantage that their power/weight and power/volume ratios are excessive and thus are too costly. Apart from this, excessive noise, unsatisfactory shifting shocks and high starting resistances (break-loose torques of the hydraulic motor) arise.